Probing the spatial structure of the Dirac vacuum via phase-controlled colliding laser pulses

Abstract

A highly charged nucleus can induce spatial structures into the otherwise spatially homogeneous Dirac quantum vacuum state. We propose that the electron-positron pair creation process triggered by two counter-propagating laser pulses can be used to probe these structures. The particle yield can be controlled by the phase relationship between the beams. Once the pulses overlap, they form standing waves whose nodal patterns are determined by this laser phase. Due to the spatial deformation of the vacuum state, the maximal pair creation yield is observed for those phases that lead to nodes (and not anti-nodes!) where the nucleus is located. This means rather counterintuitively that the particle yield is maximum, despite the fact that the electrical field intensity almost vanishes in the interaction zone.